86 THE LIFE OF PASTEUR 



The year 1859 was given up to examining further facts 

 concerning fermentation. Whence came those ferments, 

 those microscopic bodies, those transforming agents, so weak in 

 appearance, so powerful in reality? Great problems were 

 working in his mind; but he was careful not to propound them 

 hastily, for he was the most timid, the most hesitating of men 

 until he held proofs in his hands. "In experimental science, '* 

 he wrote, "it is always a mistake not to doubt when facts do not 

 compel you to affirm." 



In September he lost his eldest daughter. She died of 

 typhoid fever at Arbois, where she was staying with her grand- 

 father. On December 30 Pasteur wrote to his father; **I 

 cannot keep my thoughts from my poor little girl, so good, so 

 happy in her little life, whom this fatal year now ending has 

 taken away from us. She was growing to be such a com- 

 panion to her mother and to me, to us all. . . . But forgive 

 me, dearest father, for recalling these sad memories. She is 

 happy; let us think of those who remain and try as much as 

 lies ^n our power to keep from them the biUerness of this life. 



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